Battery charge determination

ABSTRACT

A battery charge determination device including at least one battery cell voltage measurement device, at least one battery cell internal resistance measurement device, and at least one battery charge assessment device operably connected to the at least one battery cell voltage measurement device and the at least one battery cell internal resistance measurement device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to data processing systems.

2. Description of the Related Art

Data processing systems are systems that manipulate, process, and storedata and are notorious within the art. Personal computer systems, andtheir associated subsystems, constitute well known species of dataprocessing systems.

One particularly popular type of personal computer system is theportable computer system (e.g., laptop, notebook, sub-notebook, andpalm-held computer systems). Portable computer systems allow stand-alonecomputing and typically have their own power-supplies, modems, andstorage devices.

In order to allow maximum flexibility of use, portable computer systemstypically utilize a “mix” of different types of power supplies. Forexample, a portable computer system typically has at least one externalpower supply adapter (e.g., an AC-DC adapter, or a cigarette lighteradapter), which will allow the portable computer to be powered from anexternal power outlet such as an AC wall outlet, or a cigarette lighteroutlet in an automobile. In addition, a portable computer systemtypically has at least one rechargeable battery, which serves as aninternal power supply and which allows the portable computer system tobe powered up and used in remote locations where no external powersupplies are present.

Loss of power to a data processing system can be a catastrophic event.For example, if power is lost while a personal computer user is workingon a critical document (such as an engineering schematic) stored in theRandom Access Memory (RAM) of the computer, the data in the RAM istypically lost.

When a portable computer system is utilizing battery power in a locationwhere no external power supply is readily available, loss of power dueto an expended battery can be catastrophic. Accordingly, most portablecomputer systems provide special battery monitoring equipment (e.g.,hardware and/or software and/or firmware) which gauges how much batterypower the portable computer systems have at any particular point intime. Additionally, in an effort to avoid a catastrophic loss of datadue to loss of power arising from an expended battery, power downutilities (e.g., programs) observe the special battery monitoringequipment and automatically perform a “suspend to disk” (i.e., save thestate of the personal computer to disk) and subsequent immediate powerdown when battery power is sensed as being at a dangerously low level.

One common type of special battery monitoring equipment is known in theart as a “coulomb counter,” which essentially keeps track of the inflowand outflow of electric energy from a battery. Batteries store energy inthe form of electric charges, which are typically denoted in units ofcoulombs. A coulomb counter first determines the number of coulombswhich are “loaded” into a battery by a battery charger. The chargeloaded into the battery is typically determined by multiplying measuredaverage current, delivered by the battery charger to the battery by thetime interval, expressed in seconds, during which the measured averagecurrent was delivered. That is, since one ampere is roughly one coulombper second, the net charge transferred can be roughly calculated bymultiplying average charger-to-battery current by the time it wasflowing (e.g., coulombs=seconds×coulombs/second). Thereafter, thecoulomb counter keeps a running aggregate total of the charge extractedfrom the battery using the same coulomb counting mechanism. That is, anaggregate count is kept of charge leaving the battery where the chargeleaving the battery during any interval of time is calculated bymultiplying measured average current out of the battery by the time thecurrent is flowing out of the battery. Since an aggregate count is keptof the charge leaving the battery, the coulomb counter can be used toalert the system when charge out of the battery is approaching thecharge loaded into the battery.

Notice that the foregoing is not actually measuring charge in thebattery, but is merely assuming that a battery contains a total chargedelivered during an interval of charging. It is very common for apartially charged battery to be connected to a battery charger. Sincethe battery already contains a certain amount of stored charge, thecoulombs “in,” as read by the coulomb counter, will actually be lessthan the charge ultimately stored in battery (because the battery hasthis charge in, plus the battery's initial partial stored charge). Ithas been found empirically that repeated occurrences of the foregoingscenario (charging a partially charged battery) can “confuse” thecoulomb counter as to the actual amount of charge available, which canlead to malfunctions (e.g., showing a low battery condition when none infact exists, or, in some instances, immediately suspending to disk whenbattery power is accessed, essentially rendering the system's batteryunusable).

Another type of problem that can occur with special battery monitoringequipment utilizing coulomb counting is related to loss of capacity as abattery ages. Those skilled in the art will recognize that a batterystored at full charge over a long period of time will typically lose itsability to store charge. Consequently, whereas the coulomb count intothe battery might indicate that a given amount of charge is available inthe battery, in point of fact, due to aging and physical changes withinthe battery, the actual charge which can be ejected from the battery isactually much less.

Accordingly, the decreased capacity battery will actually run out ofenergy while the coulomb counter still shows plenty of charge residentwithin the battery. This can cause loss of power with relatively nowarning, which can be catastrophic in a data processing system context.

Another common type of special battery monitoring equipment keys off thevoltage of the battery. That is, when the voltage drops to a certainpre-specified level, special battery monitoring equipment assumes a lowpower condition exists. This type of special battery monitoringequipment is particularly prone to error in that variability inbatteries can result in a relatively low battery voltage, when in fact asignificant amount of energy is still stored in the battery. Thus, a lowbattery condition may be detected when in fact there is actually plentyof energy stored in the battery. The converse is also true, for reasonssimilar to those discussed above. That is, the battery might show afully charged voltage, but, due to loss of capacity associated withaging, run out of energy even though its measured voltage is withintolerance.

Accordingly, it is apparent from the foregoing that there is a need inthe art for method and device which give an accurate assessment ofenergy stored in a battery, such as a data processing system battery.

SUMMARY OF THE INVENTION

A method and device have been discovered which give an accurateassessment of energy stored in a battery, such as a data processingsystem battery. In one embodiment, a method for determining storedcharge in a battery includes but is not limited to measuring an internalresistance of a battery cell, measuring a voltage of the battery cell,and, assessing—in response to the internal resistance and voltage of thebattery cell—the charge stored in the battery.

In one embodiment, a battery charge determination device includes, butis not limited to, at least one battery cell voltage measurement device,at least one battery cell internal resistance measurement device, and atleast one battery charge assessment device operably connected to the atleast one battery cell voltage measurement device and the at least onebattery cell internal resistance measurement device.

In one embodiment, a data processing system includes, but is not limitedto, at least one battery operably coupled to the data processing system,and a battery charge determination device which includes but is notlimited to (1) at least one battery cell voltage measurement device, and(2) at least one battery cell internal resistance measurement device,and (3) at least one battery charge assessment device operably connectedto the at least one battery cell voltage measurement device and the atleast one battery cell internal resistance measurement device.

In one embodiment, a method of manufacturing a battery chargedetermination device includes, but is not limited to, operably couplinga voltage waveform generator to a first battery cell terminal,connecting voltage measuring circuitry to the first battery cellterminal, and operably coupling a current sensing device to a secondbattery cell terminal.

The foregoing is a summary and thus contains, by necessity,simplifications, generalizations, and omissions of detail; consequently,those skilled in the art will appreciate that the summary isillustrative only and is not intended to be in any way limiting. Otheraspects, inventive features, and advantages of the present invention, asdefined solely by the claims, will become apparent in the non-limitingdetailed description set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood, and its numerousobjects, features, and advantages made apparent to those skilled in theart by referencing the accompanying drawings.

FIG. 1 depicts data processing system 100 in which an embodiment of thepresent invention may be practiced.

FIG. 2 shows a partially schematic idealized representation of batterycharge determination device 250 which determines the charge of batterycell 204 utilizing battery cell's 204 measured internal resistance andvoltage.

FIG. 3 depicts a high-level logic flowchart which can be used to obtainand construct tabular data set 254, as shown in FIG. 2.

FIG. 4 illustrates a high-level logic flowchart which shows how oneembodiment of the data gathered via the process(s) described withrespect to FIG. 3 and the measurements described with respect to FIG. 2can be utilized to give an accurate gauge of battery energy available.

FIG. 5 shows a highlevel schematic diagram showing an alternativeembodiment of battery charge determination device 250 where thealternative embodiment provides for determining battery charge inbatteries composed of one or more cells.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

The following sets forth a detailed description of a mode for carryingout embodiments described. The description is intended to beillustrative of the invention and should not be taken to be limiting.

Referring to FIG. 1, depicted is data processing system 100 in which anembodiment of the present invention may be practiced. Data processingsystem 100 includes microprocessor 105 which is coupled to cache 129 andmemory controller 110 via the processor bus (“CPU bus”) 191. Dataprocessing system 100 also includes system memory 125 of dynamic randomaccess memory (“DRAM”) modules (not shown) coupled to memory controller110. Data processing system 100 also includes Basic Input Output System(“BIOS”) memory 124 (which can contain many types of data, such assystem BIOS 155, video BIOS 161, and/or SMM code 150) coupled to localbus 120. A FLASH memory or other nonvolatile memory is used as BIOSmemory 124. BIOS memory stores the system code.

Graphics controller 115 is coupled to local bus 120 and to panel displayscreen 140. Graphics controller 115 is coupled to video memory 145 andstores information to be displayed on panel display screen 140. Paneldisplay 140 is typically an active matrix or passive matrix liquidcrystal display (“LCD”) although other display technologies may be usedas well. Also shown is graphics controller 115 coupled to optionalexternal display 156.

Bus interface controller or expansion bus controller 158 couples localbus 120 to an expansion bus, shown as an Industry Standard Architecture(“ISA”) bus, but which could be represented as a Peripheral ComponentInterconnect (“PCI”) bus. PCMCIA (“Personal Computer Memory CardInternational Association”) controller 165 is also coupled to expansionbus 160 and PCMCIA devices 170. I/O controller 175 is coupled toexpansion bus 160 as well. I/O controller 175 interfaces to IntegratedDrive Electronics (“IDE”) hard drive 180 and to floppy drive 185.Keyboard Interface 102 is coupled to expansion bus 160 and further iscoupled to keyboard 122 and auxiliary device 127; alternatively,keyboard 122 and auxiliary device 127 are shown to couple directly toexpansion bus 160.

Data processing system 100 includes battery charge determination device250, which monitors charge stored in battery 102, which may be a singlecell or multi-cell battery. Depicted is that battery chargedetermination device 250 is in communication with power managementmicrocontroller 108. Battery charge determination device 250 determinesthe charge stored in battery 102 and outputs that charged storedinformation to various recipients that have need for such information(e.g., a battery power display device, a program which creates agraphical icon on panel display screen 140, or a power management entitythat monitors for a low battery condition and performs automaticpowerdown) by and through power management microcontroller 108 (althoughmany other types of data paths and connections are possible). It will beappreciated in the art that data processing system 100 could be othertypes of computer systems, such as desktop, workstation, or networkserver computers. However, in the embodiment shown data processingsystem 100 is depicted as a portable or notebook computer. Thus, battery102 would typically be a rechargeable battery, such as Nickel Cadmium(“NiCad”), Nickel Metal Hydride (“NiMH”), or Lithium-Ion (“Li-Ion”).Power management microcontroller 108 controls the distribution of powerto different devices. Power management microcontroller 108 is coupled tomain power switch 112 that the user actuates to turn the computer systemon and off. When power management microcontroller 108 powers down otherparts the of data processing system 100 to conserve power, powermanagement microcontroller 108 remains coupled to a source of power.

Power management microcontroller 108 is coupled to battery chargingapparatus 164. Battery charging apparatus 164 is coupled to batterycharge determination device 250. Battery charging apparatus 164 iscapable of charging battery 102. Power management microcontroller 108couples to power management chip set 118, which couples to Real TimeClock (RTC) 142, which couples to I/O controller 175.

Referring now to FIG. 2, shown is a partially schematic idealizedrepresentation of battery charge determination device 250 whichdetermines the charge of battery cell 204 utilizing battery cell's 204measured internal resistance and voltage. Shown is voltage waveform 200,which is depicted as an idealized 1 KHz square wave with a duty cycle of50%. For sake of illustration, voltage waveform 200 is depicted as beinggenerated by switch 202 within circuit 201.

During the first half of its duty cycle, t_(H), voltage waveform 200 isshown to be at source voltage V_(H), which is at some voltage in excessof the charged voltage, V_(batt), on battery cell 204. During t_(h),while voltage waveform 200 is at its maximum V_(H), battery cellinternal resistance measurement device 251 measures the internalresistance of battery cell 204. In one embodiment, this is accomplishedas follows.

Voltage waveform 200, during the first half of the duty cycle, is shownto be at its maximum V_(H), which for sake of illustration is depictedas source 205 voltage V_(H) in circuit 201; V_(H) is some voltage higherthan the expected maximum charge voltage on battery cell 204. SinceV_(H) is higher than V_(batt) current will flow from source 205 ofvoltage V_(H), through battery cell 204, then through sense resistor206, and then back into the negative terminal of source 205 of voltageV_(H). Voltmeter 208, which is depicted as having relatively infiniteimpedance (and thus relatively no effect on the operation of circuit201), measures the voltage across sense resistor 206. Thereafter, sincethe resistance of sense resistor 206 and the voltage across senseresistor 206 are known, shown is that the current through sense resistor206 can be calculated. Substantially simultaneously with the foregoingmeasurements and subsequent calculations (i.e., during t_(H) wherevoltage waveform 200 has value V_(H)), voltmeter 209 measures voltage,B_(batt), across battery cell 204. Thereafter, shown is that since thesame current in sense resistor 206 flows through series connectedbattery cell 204, the measured voltage, V_(batt), across battery cell204 can be used to calculate the internal resistance, R_(IB), of batterycell 204. Depicted is that the calculated internal resistance, _(RIB),is delivered to battery charge assessment device 252.

During the second half of its duty cycle, t_(L), voltage waveform 200 isshown to be at its minimum, which for sake of illustration is depictedas source 207 voltage V_(L) in circuit 201; V_(L) is some voltage lessthan the expected minimum charged voltage on battery cell 204. Duringthe second half of the duty cycle of voltage waveform 200, since source207 voltage V_(L) is at a voltage lower than B_(batt), depicted is thatcurrent will flow from the positive terminal of B_(batt), through source207 of voltage V_(L), then through sense resistor 206, and then backinto the negative terminal of battery cell 204. At some point duringt_(L), while voltage waveform 200 is at its minimum V_(L), voltmeter 209is used to measure the voltage V_(batt) on battery cell 204. (It hasbeen found empirically that measuring V_(batt) battery cell 204 asdescribed, when driven by an alternating current such as that generatedby voltage waveform 200, is much more likely to actually capture thetrue charge voltage on battery cell 204. One reason for this is thatdriving the battery with an alternating current such as that generatedby voltage waveform 200 (which in one embodiment is a 1 KHz square wave)tends to alleviate the problems associated with “polarization” (anincrease or decrease in battery voltage not due to actual stored energyin a battery, particularly apparent in Lithium-Ion batteries) in thatthe alternating current waveform allows the voltage on battery cell 204to be measured before the battery has a chance to polarize.) Subsequentto measurement, the measured voltage of battery cell 204 is delivered tobattery charge assessment device 252.

Illustrated is that the internal resistance of battery cell 204 and themeasured voltage of battery cell 204 are delivered to battery chargeassessment device 252. Thereafter, shown is that battery chargeassessment device 252 compares the measured voltage and measuredinternal resistance of battery cell 204 with tabular data set 254 havingrow and column entries correlating measured battery voltage and internalresistance with charge actually stored in a battery (in one embodiment,tabular data set 254 is stored in a memory associated with battery cell204). Depicted is that battery charge assessment device 252 retrievesfrom the table the stored charge value residing in the row (Voltage) andcolumn (Resistance) entry which best match with the measured voltage,V_(batt), and measured internal resistance, R_(IB), of battery cell 204.Thereafter, shown is that battery charge assessment device 252 assessesthe stored charge in battery cell 204 to be the retrieved chargeQ_(row,column). Battery charge assessment device 252 thereafter outputsthe value of the stored charge in battery cell 204 to a component of adata processing system sensitive to the stored charge in the battery,such as a display device which tracks and displays the stored charge inthe battery, an application problem driving a display device showing thestored charge in the battery, or a battery charge monitoring programwhich detects a low battery condition and shuts down a data processingsystem to avoid lost data.

In an idealized situation, the measured voltages and resistances ofbattery cell 204 in response to both voltage V_(H) and V_(L) wouldalways be the same. However, those skilled in the art will appreciatethat in a real-world (as opposed to a mathematically ideal circuit) themeasured voltages and resistances can vary in response to voltage V_(H)and V_(L), and can even vary across duty cycles. Accordingly, themeasured voltages and resistances of battery cell 204 can be gatheredacross several duty cycles to generate some type of average of themeasured voltages and internal resistances of battery cell 204. Theexact number of duty cycles used to do this is a design choice withinthe purview of the system designer.

With reference now to FIG. 3, depicted is a high-level logic flowchartwhich can be used to obtain and construct tabular data set 254, as shownin FIG. 2. Method step 300 shows the start of the process. Method step302 depicts the charging of a battery for some interval of timet_(charge) (e.g., for the interval of time required to charge thebattery to its maximum charged value). Method step 304 shows measuringthe internal resistance of the battery as described in relation to FIG.2 (i.e., measuring the internal resistance of the battery during themaximum value V_(H) of a square wave waveform). Method step 306illustrates measuring the voltage of the charged battery as described inrelation to FIG. 2 (i.e., measuring the voltage across the batteryduring the minimum value V_(L) of a square wave waveform).

Once the voltage of the charged battery and the internal resistance ofthe charged battery have been measured, method step 307 shows that themeasured voltage and internal resistance of the charged battery arestored in a table, often in a memory (e.g., a RAM or ROM) which isintegrated into a case containing the battery. Thereafter, method step308 illustrates connecting the charged battery to a load similar to aload (e.g., data processing system 100) expected to be driven by thebattery in an everyday environment and simultaneously starting a timer.Method step 310 shows measuring the aggregate charge leaving thebattery, which in one embodiment is accomplished via coulomb counting.

Method step 312 depicts determining if the battery has been depleted(e.g., has battery power dropped to such a low level that dataprocessing system 100 being driven by the battery can no longer performspecified actions, such as accessing the hard drive). In the event thatthe battery has not been depleted, the process “loops” back to methodstep 310.

In the event that the inquiry of method step 312 indicates that thebattery has been depleted, the process proceeds to method step 314,which shows that the recorded aggregate charge which has left thebattery during discharge is recorded as the tabular entry associatedwith the measured internal resistance of the battery and measuredvoltage on the battery which were illustrated as being stored as row andcolumn values in method step 307. Thereafter, method step 316 depictsthat the process stops.

In one implementation, the foregoing described process of FIG. 3 isrepeated for varying values (i.e., for varying periods of time thebattery is on the charger) of charge within the battery. The actualnumber of values obtained is a design choice within the purview of thesystem designer. However, upon completion of the series of tests, theresults will be such that an internal impedance and voltage on thebattery can be paired with the charge in the battery. Such informationallows the accurate “gauging” of charge left in the battery in a mannerwhich will be described in relation to FIG. 4, below. In anotherembodiment, the stored charge values are obtained by (1) fully charginga battery, (2) measuring and recording the voltage and internalresistance of the battery, and (3) incrementally discharging thebattery, with measured battery internal impedance and voltage beingrecorded after each incremental discharge. A coulomb counter (whichtypically is not a separate counter, but rather amounts to startinganother count, associated with the measured voltage and internalresistance of the battery after the incremental discharge, at zero) isstarted after each incremental discharge and associated with themeasured battery internal resistance and voltage which are measuredimmediately subsequent to the incremental discharge; all such coulombcounters (i.e., those associated with particular measured values ofbattery internal resistance and voltage) are allowed to run until thebattery is completely discharged. Thus, at the end of one discharge, thetable correlating measured internal resistances and measured batteryvoltages can be constructed since each of the individual coulombcounters will have contained a measured coulomb count for each measuredvalue of the internal resistance of the battery and the voltage of thebattery which were taken at the end of each incremental discharge.

While the alternate method of charging usually allows the table to beconstructed in a shorter period of time, the process in FIG. 3 waspresented in that it is easier to understand and because it will tend toproduce a somewhat more accurate count of energy discharged, since itavoids leakage while measurements are taken during the alternativeincremental discharge process.

Referring now to FIG. 4, depicted is a high-level logic flowchart whichshows how in one embodiment the data gathered via the process(s)described with respect to FIG. 3, and the measurements described withrespect to FIG. 2, can be utilized to give an accurate gauge of batteryenergy available. Method step 400 shows the start of the process. Methodstep 402 depicts the step of connecting a voltage waveform generator,capable of generating a voltage waveform such as voltage waveform 200 toa battery (such as battery cell 204). Method step 404 illustrates that,subsequent to the connection of the voltage waveform generator to thebattery, measurements analogous to those described in relation to FIG. 2are taken of the internal resistance and voltage of the battery.Thereafter, method step 406 shows that the measured internal resistanceand voltage of the battery are compared to a table of data containingdata coordinating a measured voltage and resistance of a battery withthe amount of energy stored in the battery (e.g., tabular data set 254).Method step 408 depicts that the energy stored is retrieved from thetable entry having values most closely approximating the measuredvoltage and resistance of the battery. Method step 410 illustrates thatthe retrieved energy stored amount is then output; the output can bedelivered to many different recipients, such as a display, anotherprogram driving a display (e.g., a gas gauge graphical user interfaceprogram), or a program monitoring the system for low battery conditions.Thereafter, method step 412 shows the end of the process.

With reference now to FIG. 5, shown is a high-level schematic diagramshowing alternative battery charge determination device 250 fordetermining battery charge in batteries composed one or more cells.Depicted is battery Microcontroller Unit (MCU) 502 which providescontrol to the various aspects of the circuit shown as will now bedescribed. Shown is that MCU 502 is connected to discharge control powerField Effect Transistor (FET) 504 and charge control power FET 506.These FETs 504 and 506 are typically used to control the charging ordischarging of battery 508 composed of cells 204, 510, 512, and 514arranged in series. However, in order to determine the charge of battery508, discharge control power FET 504 and charge control power BET 506are both turned off, thereby isolating alternative battery chargedetermination device 250 from the ordinary loading and chargingcircuitry (not shown) of battery 508.

With battery charge determination device 250 so isolated, calibrationenable FET 552 is activated such that pulse current source 550, whichproduces a squarewave waveform analogous to waveform 200, except that inthis instance V_(H) is to be higher than the highest expected chargedvoltage of battery 508 (i.e., the entire series combination of voltageson cells 204, 510, 512, and 514) and V_(L) is to be less than the lowestexpected charge voltage of battery 508 (i.e., the entire seriescombination of voltages on cells 204, 510, 512, and 514). Pulse currentsource 550, through activated calibration enable FET 552 is connected tothe positive terminal of battery 508. Thereafter, the voltage andinternal resistance of each of cells 204, 510, 512, and 514 of battery508 are sequentially tested (battery cell 204 is depicted as being acell of battery 508 for ease of understanding and for easilycoordinating the discussion of the circuit of FIG. 5 with the discussionof the circuit of FIG. 2). This is done by essentially repeating thetesting process described in relation to FIG. 5 for each of theindividual cells 204, 510, 512, and 514 of battery 508. For example, totest battery 508, MCU 502 during a time interval t_(H) wherein thewaveform produced by pulse current source 550 is at its maximum valueV_(H) determines the current through sense resistor 206 (and hencethrough battery 508 and individual cells 204, 510, 512, and 514).Thereafter, during the next time interval t_(L) MCU 502 determines thevoltages, internal resistances, and energy stored in individual cells204, 510, 512, and 514 of battery 508 in rapid succession. Thereafter,the stored charges of individual cells 204, 510, 512, and 514 of battery508 can be summed to get the total charge stored in battery 508.

To test battery cell 204, MCU 502, during a time interval t_(L) at whichthe waveform pulse current source 550 is at a voltage minimum V_(L),directs analog MUX 516 (which is a type of integrated circuit having abuilt-in voltage meter, such MUXes being known in the art) to connectacross the positive terminal of battery cell 204 and the negativeterminal of battery cell 204, read or measure the voltage across batterycell 204, and deliver the measured voltage over cell voltage measurementline 518 to MCU 502. MCU 502 then uses the measured voltage and thepreviously determined current value gleaned via use of sense resistor206 to calculate the internal resistance of battery cell 204. Thedetermined internal resistance and voltage of battery cell 204 are thenutilized to determine the energy stored in battery cell 204 via a tablelook-up process substantially similar to those described in relation toFIGS. 2 and 4. Thereafter, the energy stored in battery cell 204 issaved in a memory of MCU 502.

Subsequent to the determination of energy stored in battery cell 204,and during the time interval t_(L), MCU 502 directs analog MUX 516 toconnect across the positive terminal of battery cell 510 and thenegative terminal of battery cell 510. Thereafter, the internalresistance and voltage of battery cell 510 is determined utilizing aprocess substantially similar to that described for cell 204 of battery508 (i.e., utilizing the measured voltage across battery cell 510 andthe previously determined current value gleaned utilizing sense resistor206 in order to ultimately determine the charge stored in battery 510via look-up table reference). Thereafter, the energy stored in batterycell 510 is added to the previously stored count of the energy stored inbattery cell 204 and the total resulting from the addition is saved in amemory of MCU 502.

Subsequent to the determination of energy stored in battery cell 204 andbattery cell 510, and during the time interval t_(L), MCU 502 directsanalog MUX 516 to connect across the positive terminal of battery cell512 and the negative terminal of battery cell 512. Thereafter, theinternal resistance and voltage of battery cell 512 is determinedutilizing a process substantially similar to that described for batterycell 204 of battery 508 (i.e., utilizing the measured voltage acrossbattery cell 512 and the previously determined current value gleanedutilizing sense resistor 206 in order to ultimately determine the chargestored in battery cell 512 via look-up table reference). Thereafter, theenergy stored in battery cell 512 is added to the previously storedcount of the energy stored in battery cell 204 and battery cell 510 andthe total resulting from the addition is saved in a memory of MCU 502.

Subsequent to the determination of energy stored in battery cell 204,battery cell 510, and battery cell 512, and during the time intervalt_(L), MCU 502 directs analog MUX 516 to connect across the positiveterminal of battery cell 514 and the negative terminal of battery cell514. Thereafter, the internal resistance and voltage of battery cell 514is determined utilizing a process substantially similar to thatdescribed for battery cell 204 of battery 508 (i.e., utilizing themeasured voltage across battery cell 514 and the previously determinedcurrent value gleaned utilizing sense resistor 206 in order toultimately determine the charge stored in battery cell 514 via look-uptable reference). Thereafter, the energy stored in battery cell 514 isadded to the previously stored count of the energy stored in batterycell 204, battery cell 510 and battery cell 512 and the total resultingfrom the addition is saved in a memory of MCU 502.

Since individual battery cells 204, 510, 512, and 514 make up battery508, the sum total of their individual energies equates to the energystored in battery 508. Accordingly, this sum can be passed by MCU 502 toother display devices or programs in a manner analogous to thatdescribed in relation to method step 410.

Notice that although the foregoing described the determination of theenergy stored in a battery made up of four cells, the example discussedabove can be easily generalized to a battery composed of N (where N issome positive integer) number of cells. In addition, as discussed above,each battery can have associated with it a lookup table, which can bestored either in MCU 502 memory or in on-battery memory such that it isaccessible to MCU 502.

The above description is intended to be illustrative of the inventionand should not be taken to be limiting. Other embodiments within thescope of the present invention are possible. Those skilled in the artwill readily implement the steps necessary to provide the structures andthe methods disclosed herein, and will understand that the processparameters and sequence of steps are given by way of example only andcan be varied to achieve the desired structure as well as modificationsthat are within the scope of the invention. Variations and modificationsof the embodiments disclosed herein may be made based on the descriptionset forth herein, without departing from the spirit and scope of theinvention as set forth in the following claims.

Other embodiments are within the following claims.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art that,based upon the teachings herein, changes and modifications may be madewithout departing from this invention and its broader aspects and,therefore, the appended claims are to encompass within their scope allsuch changes and modifications as are within the true spirit and scopeof this invention. Furthermore, it is to be understood that theinvention is solely defined by the appended claims It will be understoodby those within the art that if a specific number of an introduced claimelement is intended, such an intent will be explicitly recited in theclaim, and in the absence of such recitation no such limitation ispresent. For non-limiting example, as an aid to understanding, thefollowing appended claims may contain usage of the introductory phrases“at least one” and “one or more” to introduce claim elements. However,the use of such phrases should not be construed to imply that theintroduction of a claim element by the indefinite articles “a” or “an”limits any particular claim containing such introduced claim element toinventions containing only one such element, even when same claimincludes the introductory phrases “one or more” or “at least one” andindefinite articles such as “a” or “an”; the same holds true for the useof definite articles used to introduce claim elements.

What is claimed is:
 1. A method of determining the capacity of abattery, the method comprising: (a) applying a first voltage to thebattery during a first interval; (b) acquiring battery operational dataduring the first interval; (c) applying a second voltage to the batteryduring a second interval; (d) acquiring battery operational data duringthe second interval; (e) determining a value of a first batterycharacteristic from the battery operational data that is acquired duringthe first interval; and (f) determining a value of a second batterycharacteristic from the battery operational data that is acquired duringthe second interval.
 2. A method as defined in claim 1, furthercomprising: based on the value of the first battery characteristic andon the value of the second battery characteristic, reading acorresponding battery capacity from a compilation of battery capacitydata.
 3. A method as defined in claim 2, wherein the first voltage is avoltage that is greater than an expected fully-charged battery voltageand the second voltage is a voltage that is less than an expectedfully-discharged battery voltage.
 4. A method as defined in claim 3,wherein the first battery characteristic is battery internal resistance.5. A method as defined in claim 4, wherein the second batterycharacteristic is battery voltage.
 6. A method as defined in claim 5,wherein battery capacity data are stored in a two-dimensional matrix andbattery capacity values in the matrix correlate to respective valuepairs comprising a value of battery internal resistance and a value ofbattery voltage.
 7. A method as defined in claim 6, wherein a batterycapacity is read by matching determined values of battery internalresistance and battery voltage to matrix values of battery internalresistance and battery voltage.
 8. A method as defined in claim 1,wherein steps (a), (c) and (e) are performed repeatedly and an averagevalue of the first battery characteristic is determined.
 9. A method asdefined in claim 8, wherein steps (b), (d) and (f) are performedrepeatedly and an average value of the second battery characteristic isdetermined.
 10. A method as defined in claim 9, wherein based on theaverage value of the first battery characteristic and on the averagevalue of the second battery characteristic, a corresponding batterycapacity is read from a compilation of battery capacity data.
 11. Amethod as defined in claim 10, wherein the first voltage is a voltagethat is greater than an expected fully-charged battery voltage and thesecond voltage is a voltage that is less than an expectedfully-discharged battery voltage.
 12. A method as defined in claim 11,wherein the first battery characteristic is battery internal resistance.13. A method as defined in claim 12, wherein the second batterycharacteristic is battery voltage.
 14. A method as defined in claim 13,wherein battery capacity data are stored in a two-dimensional matrix andbattery capacity values in the matrix correlate to respective valuepairs comprising a value of battery internal resistance and a value ofbattery voltage.
 15. A battery charge determination device comprising:first means for applying a first signal level to a battery during afirst interval and for applying a second signal level to the batteryduring a second interval; second means for determining a value of afirst battery characteristic from battery operational data acquiredduring the first interval; third means for determining a value of asecond battery characteristic from battery operational data acquiredduring the second interval; and a memory device that stores batterycharge data that corresponds to values of the first batterycharacteristic and values of the second battery characteristic.
 16. Abattery charge determination device as defined in claim 15, wherein thefirst signal level is a voltage that is greater than an expectedfully-charged battery voltage and the second signal level is a voltagethat is less than an expected fully-discharged battery voltage.
 17. Abattery charge determination device as defined in claim 16, wherein thefirst battery characteristic is battery internal resistance.
 18. Abattery charge determination device as defined in claim 17, wherein thesecond battery characteristic is battery voltage.
 19. A battery chargedetermination device as defined in claim 18, wherein battery charge dataare stored in a two-dimensional matrix and battery charge values in thematrix correlate to respective value pairs comprising a value of batteryinternal resistance and a value of battery voltage.
 20. A battery chargedetermination device as defined in claim 15, wherein the memory devicestores battery charge data in an array that includes columns and rows,wherein each column corresponds to a value of the first batterycharacteristic and each row corresponds to a value of the second batterycharacteristic.
 21. A battery charge determination device as defined inclaim 20, wherein the first battery characteristic is battery internalresistance and the second battery characteristic is battery voltage. 22.A battery charge determination device as defined in claim 21, whereinthe second means includes a resistor for sensing a battery current. 23.A battery charge determination device as defined in claim 22, whereinthe third means includes a voltmeter for measuring a battery voltage.24. A battery charge determination device as defined in claim 20,wherein battery charge data entries in the array are determined by: (a)applying a first voltage to the battery during a first interval; (b)acquiring battery operational data during the first interval; (c)applying a second voltage to the battery during a second interval; (d)acquiring battery operational data during the second interval; (e)determining a value of a first battery characteristic from the batteryoperational data that is acquired during the first interval; and (f)determining a value of a second battery characteristic from the batteryoperational data that is acquired during the second interval.
 25. Acomputer system comprising; a processor; power management means coupledto the processor for monitoring a battery condition and respondingthereto; and a battery charge determination device coupled to the powermanagement means, the battery charge determination device COMPRISING:first means for applying a first signal level to a battery during afirst interval and for applying a second signal level to the batteryduring a second interval; second means for determining a value of afirst battery characteristic from battery operational data acquiredduring the first interval; third means for determining a value of asecond battery characteristic from battery operational data acquiredduring the second interval; and a memory device that stores batterycharge data that corresponds to values of the first batterycharacteristic and values of the second battery characteristic.
 26. Acomputer system as defined in claim 25, wherein the memory device storesbattery charge data in an array that includes columns and rows, whereineach column corresponds to a value of the first battery characteristicand each row corresponds to a value of the second batterycharacteristic.
 27. A computer system as defined in claim 26, whereinthe first battery characteristic is battery internal resistance and thesecond battery characteristic is battery voltage.
 28. A computer systemas defined in claim 27, wherein the second means includes a resistor forsensing a battery current.
 29. A computer system as defined in claim 28,wherein the third means includes a voltmeter for measuring a batteryvoltage.